1. Field of the Invention
The present invention relates to a display panel device including a flat display panel and a front sheet that is glued on the display panel.
2. Description of the Prior Art
Technology development of a plasma display panel (PDP) that is a self-luminous device is directed to a large screen for providing more powerful display. One of the important tasks for a large screen is weight reduction of the panel.
In general, a display device including a plasma display panel has a filter plate having a base of a tempered glass. This filter plate is arranged in front of the plasma display panel with air gap. The filter plate has various functions of adjusting a display color optically, preventing reflection of external light, shielding electromagnetic waves, and shielding near infrared rays concerning displaying operation and a function of protecting the plasma display panel mechanically. In addition, arranging the filter plate in front of the plasma display panel is also effective for sound isolation of vibrational sounds generated by the plasma display panel.
However, the filter plate is not desired for a large screen of the plasma display panel because it has a large weight. In order to reduce a weight of the display device, another structure is suitable in which a thin filter having a base of a resin film is glued directly on the front face of the plasma display panel instead of attaching the filter plate. Japanese unexamined patent publication No. 2001-343898 discloses a front filter that includes a transparent conductive film for a measure against EMI and a anti-reflection film that is glued on the front side of the front filter.
When a thick transparent sheet is glued on the front face of the plasma display panel, light from the screen is scattered at the surface of the sheet (i.e., an interface between the sheet and air) that is farther than the surface of the panel. As a result, a phenomenon in which a contour of the highlight portion of the image may be blurred, which is called a “halation” becomes conspicuous. In addition, microscopic asperities on the front surface of the sheet may cause distortion of a reflected image of the external light.